The goal of the project is to complete the initial development of growth- sensitive measures of non-verbal cognitive abilities for assisting mental health professionals in decision making, treatment planning and assessment for the estimated three million children, adolescents and adults with significant cognitive disabilities. Currently, no adequate device exists to measure "growth" (the small increments of improvement) of cognitive functioning in individuals diagnosed with moderate cognitive delays and traumatic brain injury (TBI), as recently defined in the Individuals with Disabilities Education Act. Using modern cognitive-component theory and item-response theory (IRT) technology, development of easily used and readily interpretable scales will be initiated. Three research studies are proposed for Phase I: (1) psychometric studies of preliminary growth scales (e.g., reliability and fit to IRT models). (2) experimental inducement of cognitive change to test the sensitivity of the scales; and (3) examination of the classification accuracy of the scales in differentiating children with and without cognitively delays. During Phase II, the project will be expanded to include large nationally representative samples of children, adolescents and adults with a broader array of cognitive disabilities or underachievement (e.g., due to communication disorders, attention-deficits, cultural disadvantage or second-language background).